Distillation: processes – separatory – With disparate physical separation – Utilizing liquid-liquid extracting of distillation product
Patent
1996-10-02
1998-05-12
Bhat, Nina
Distillation: processes, separatory
With disparate physical separation
Utilizing liquid-liquid extracting of distillation product
203 73, 203 87, 2021851, 2021855, 2021856, B01D 1100, B01D 300
Patent
active
057500088
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to the extraction treatment of liquid or in particular solid samples in which a substance is bound. This substance is to be extracted by means of the extraction treatment, i.e. dissolved out or washed out. For the extraction, a gaseous or in particular liquid solvent is used. An extraction using gas takes place for example upon the "drying" of a sample. Here, an inert gas or air serves as a transport medium for water vapour which, upon heating of the sample, is formed in the sample from the water bound in the sample.
DESCRIPTION OF THE RELATED ART
In the case of extraction in the laboratory, as a rule one works with a liquid (at normal pressure) solvent. The liquid solvent is brought into contact with the sample in a heatable chamber. The heatable chamber may be an oven heatable with microwaves. Heating is expedient or even necessary, because the substance to be extracted can as a rule be more easily dissolved out from the sample at higher temperatures and because the solvent can take up a larger quantity of the material to be extracted at higher temperatures (dissolving power increases with the temperature).
Since the solvent is expensive and in most cases toxic (poisonous), one is concerned to recover this solvent after an extraction treatment for reasons of economy and/or for the purpose of avoiding damage to the environment or to health. A known process and a known device for this purpose are described in DE 42 23 116A1. With this known process or device the heatable chamber is evacuated by means of an evacuation line leading to the outside of the heating device to a pump, whereby the gaseous solvent evacuated off is first cooled in a condensate cooler and--so far as this is possible at the evacuation under-pressure--transformed into the liquid phase before it reaches the pump. The solvent condensate recovered by these means, which is subject to under-pressure in the condensate cooler, can be brought again to normal pressure after the process has been terminated and employed again for an extraction treatment. For this purpose, it is placed into an solvent container out of which the solvent is then drawn off by a solvent pump, e.g. a tube pump, and introduced into the heatable chamber, preferably in such a manner that the solvent drips on to the sample.
With this known process or device it is important that the pump--which generates the under-pressure upon drawing off of the solvent out of the heatable chamber--is arranged after the condensate cooler in the direction of flow. Atmospheric pressure prevails at the output of the pump.
A disadvantage of this known technique consists in that the efficiency of the recovery of the solvent is low. From DE 41 14 525A1 and from the earlier patent application of the present applicant P 44 09 887.4 there can be understood in each case a process and a device for the extraction of samples whereby the extraction is effected on the one hand at an over-pressure in a pressure resistant container and on the other hand by means of a Soxhlet apparatus arranged in the pressure container, in a circulation restricted on the one hand to the interior of the pressure container and on the other hand also restricted in time. With this technique, the solvent reaches the sample, placed in a special sample container, from above, whereby the solvent enriched with the extracted substance flows through a lower through-flow or outlet of the sample container into a chamber located beneath the sample and collects there. Further, with this technique, the solvent with the substance to be extracted is moved in the internal circulation by means of the Soxhlet apparatus and is enriched with the extracted material to a large measure. Here, the solvent located beneath the sample is heated and therewith evaporated and the rising solvent vapor is condensed above the sample by means of a cooling device, whereby the vapor--again in liquid form, drops onto the sample and again dissolves out the substance to be extracted from the sample. With this known t
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